1. Field of the Invention
The present invention relates to a flat panel display, and more particularly, to a source driver and method of driving a source line in a flat panel display.
2. Description of the Related Art
Flat panel displays include a thin film transistor (TFT) liquid crystal display (LCD), an electro-luminance flat panel display, a super twisted nematic (STN) LCD, a plasma display panel, and the like. Among these, the TFT LCD, is presently the most widely used.
FIG. 1 is a block diagram of a TFT LCD panel and its peripheral circuits. The TFT LCD panel 110 includes upper and lower plates to which a plurality of electrodes are provided to generate electric fields, a liquid crystal layer interposed between the upper and lower plates, and polarization plates attached on the upper and lower plates. The brightness of the TFT LCD 100 is adjusted by applying voltages corresponding to the gray levels to the pixel electrodes to rearrange the liquid crystal molecules. On the lower plate is disposed a plurality of switching devices such as thin film transistors (TFTs) connected to the pixel electrodes to switch the gray voltage levels. The brightness of a pixel is adjusted by using the switching devices. The three colors red (R), green (G), and blue (B) are represented by using a color filter array provided to the pixels as shown in FIG. 2.
The TFT LCD 100 includes driver circuits having gate drivers 120 disposed on a LCD panel 110 in the horizontal direction to drive a plurality of gate lines and source drivers 130 disposed on the LCD panel 110 in the vertical direction to drive a plurality of source lines and a controller (not shown) for controlling the gate and source driver circuits 120 and 130 to apply the gray voltage levels to the pixel electrodes through switching devices. In general, the controller and the gate and source driver circuits 120 and 130 may be disposed outside of the LCD panel 110. However, in the chip on glass (COG) type, the gate and source driver circuits 120 and 130 may be disposed on the LCD panel 110.
FIG. 3 is a block diagram of a conventional source driver 130. The conventional source driver 130 includes an inversion circuit 131, a latch circuit 132, a gamma decoder 133, and a buffer 134. The block diagram of FIG. 3 shows a circuit unit for driving one source line. To drive a plurality of source lines, a plurality of the circuit units shown in FIG. 3 equal to the number of source lines may be provided. The inversion circuit 131, which receives n-bit (6-bit or 8-bit) image data, has a function of selectively inverting the image data. Image data received by the inversion circuit 131 is digital data obtained by processing the three-color signals, that is, R, G. and B data transmitted externally from a graphics card in accordance with the resolution of the LCD panel 110 by the controller. The latch circuit 132 updates its data with the data newly received from the inversion circuit 131. The gamma decoder 133 selects one of 2n analog gray voltages corresponding to the output digital value of the latch circuit 132. The analog image signal output from the gamma decoder 133 is buffered by the buffer 134 and output to the source line. The source line and the corresponding pixel on the LCD panel 110 are rapidly charged with the image signal output from the buffer 134. The pixel input with the image signal adjusts the brightness by rearranging the liquid crystal molecules in response to the corresponding gray voltage levels.
As the resolution of the LCD panel 110 increases, the number of source lines driven by the source drivers 130 increases in proportion to the resolution. In a case where a high resolution LCD panel 110 is driven by conventional source drivers 130, the number of chips of the source drivers 130 must increase in proportion to the resolution. As a result, the production costs of a large-sized high-resolution LCD panel greatly increase and the productivity thereof decreases.